1. Field of the Invention
The present invention relates generally to air conditioners for vehicles, and more particularly to such an air conditioner adapted to be mounted on the roof of a vehicle such as a bus, a motor van or the like.
2. Description of the Related Art
There are various known air conditioners adapted to be mounted on the roof of a vehicle. One such roof-mounted vehicle air conditioner is disclosed in Japanese Patent Laid-open Publication No. 59-223513 and it comprises an evaporator, a blower associated with the evaporator, a condenser and a blower associated with the condenser, all the components being housed in a frame or casing mounted on a vehicle roof.
Since the disclosed air conditioner has a total weight of 250 kg or more, the vehicle roof must be reinforced to withstand a heavy load continuously exerted thereon by the air conditioner system. Because of its heaviness, the air conditioner, since it is disposed on a rear portion of the vehicle roof, makes it necessary to enlarge the size of rear tires or to reduce the number of passenger seats at the rear portion of the vehicle.
Japanese Utility Model Laid-open Publication No. 52-43241 discloses an air conditioner suspended from the ceiling of a vehicle and includes air intake ports for introducing the outside air into the passenger compartment through the air conditioner system. However, problem particular to this air conditioner exists in that only a limited overhead space is available.
Another roof-mounted vehicle air conditioner disclosed in Japanese Utility Model Laid-open Publication No. 56-6611 includes a condenser unit and an evaporator unit disposed on the vehicle roof in a spaced relation to one another and contained in a single casing. The air conditioner further includes a heat exchanger disposed inside the vehicle in a heat-exchanging relation to the condenser, and a blower also disposed inside the vehicle for forcing the inside air to circulate within the passenger compartment. In this air conditioner, the outside air intake is not considered resulting in an undesired contamination of the inside air during operation of the air conditioner.
In a cooling operation mode, the conventional air conditioners generally circulate the inside air alone, instead of introducing the outside air into the vehicle passenger compartment. Such air circulation causes the contamination of the inside air of the vehicle passenger compartment. With this drawback in mind, there is a large demand for a roof-mounted vehicle air conditioner adopting a ventilation system wherein the outside air is introdued into the vehicle passenger compartment while the inside air is discharged from the compartment.